Tank with internal tension beams

ABSTRACT

The present application concerns a substantially prismatic tank having internal tension beams having a cross section with a web and orthogonal flanges along the edges of the web, the beams being arranged in alternate orthogonal layers and being connected to each other at at least some crossing points, wherein the beams are arranged with their flanges oriented vertically and their webs oriented horizontally.

FIELD OF INVENTION

The present invention relates to tanks for storage and transportation of fluids such as hydrocarbons, including low temperature liquefied natural gas. This includes tanks for ships and floating offshore structures exposed to wave loads as well as gravity based offshore structures and land tanks exposed to earthquakes.

BACKGROUND OF THE INVENTION

Tanks may be designed in many different configurations, such as spheres, cylinders, cones and shells in general, as well as prismatic shapes. The principal advantage of prismatic shapes is that they nest closer to each other, minimising the volume taken up by such tanks. Simple prismatic tanks are far less efficient structurally as they rely on bending action for mobilisation of strength. Shells develop strength through direct tension in the plane of the shell. This develops greater strength for the same amount of material.

A more efficient design of prismatic shapes is to incorporate internal stays (tension beams). By developing stays as the main means of restraining the internal load or pressure, such prismatic staid tanks are comparable to shell shapes in structural efficiency. WO 2006/001711 A2 discloses such tanks and is hereby incorporated by reference.

Apart from developing structural strength the stays dampen sloshing induced by wave motion. The horizontal loads on the tension stays due to sloshing are absorbed by the beams and to limit bending the beams must be connected at each intersection. The beams are organised in alternate orthogonal layers.

The current method of designing such tanks is described in WO 2006/001711 A2 and also in WO2008/103053. Tension beams with vertical webs and horizontal flanges are placed in alternate orthogonal layers. Connections between beams are made by connecting flanges above each other.

OBJECT OF THE INVENTION

The object of the current invention is to utilise the bending strength of the tension beams more efficiently when used in substantially prismatic tanks.

SUMMARY OF THE INVENTION

The invention consists of using beams with horizontal webs and vertical flanges, preferably comprising connections between said beams that are made with spacer elements capable of supporting the shear load from the transverse beams so that this load is absorbed by the transverse beams above and below, in the interior of substantially prismatic tanks. The invention is further defined by:

A substantially prismatic tank with internal tension beams having a cross section with a web and orthogonal flanges along the edges of the web, the beams being arranged in alternate orthogonal layers and being connected to each other at at least some crossing points, wherein the beams are arranged with their flanges oriented vertically and their webs oriented horizontally.

The beams are preferably connected to each other by means of spacer elements, attached to the webs of the beams.

In another preferred embodiment, the beams are connected to each other by means of spacer elements, attached to at least one of the flanges of the beams.

The spacer elements are preferably capable of supporting the shear load between the beams.

Further, the spacer elements have bending stiffness and torsional flexibility.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details of the invention will be described below with reference to the exemplifying embodiments shown schematically in the appended drawings, wherein:

FIG. 1 shows a plan view, partly in section, of a first embodiment of the invention.

FIG. 2 shows a perspective view of the embodiment shown in FIG. 1.

FIG. 3 shows a lateral view, partly in section, of an alternative embodiment of the invention.

FIG. 4 shows cross sections of alternative spacer elements for use in the embodiment shown in FIG. 3.

FIG. 5 shows a perspective view of the interior of a tank where the embodiment shown in FIG. 3 is used.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross section of two angle sections 2 anchored with bolts 3 to tension beams 1.

FIG. 2 shows a perspective view of the embodiment shown in FIG. 1, with tension beams 1 having horizontal webs, connected by an angle section 2 fastened by bolts 3.

FIG. 3 shows an alternative arrangement using spacer elements 5 to connect alternate orthogonal beams 4 with bolted or welded spacer elements 5.

FIG. 4 shows alternate cross sections of spacer elements 5.

FIG. 5 shows a perspective view of the interior of a tank featuring internal tension beams 1, connected through bolted or welded spacer elements 5. 

1. A substantially prismatic tank having internal tension beams having a H- or I-shaped cross section with a web and orthogonal flanges along the edges of the web, the beams being arranged in an assembly of horizontal, orthogonally crossing tension beams, the beams being interconnected at the crossing points, wherein said beams are arranged with their flanges oriented vertically and their webs oriented horizontally, said beams being interconnected at the at least some crossing points by spacer elements the spacer elements being attached to the web or at least one of the flanges of the beams.
 2. (canceled)
 3. (canceled)
 4. A prismatic tank according to claim 1, wherein the spacer elements are capable of supporting the shear load between the beams.
 5. A prismatic tank according to claim 1, wherein the spacer elements have bending stiffness and torsional flexibility. 